sqlhelper.cs

连接数据库的基本操作,可以作为入门的学习参考

//===============================================================================
// This file is based on the Microsoft Data Access Application Block for .NET
// For more information please go to 
// http://msdn.microsoft.com/library/en-us/dnbda/html/daab-rm.asp
//===============================================================================

using System;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Collections;


namespace SQLServerDAL 
{

	/// <summary>
	/// The SqlHelper class is intended to encapsulate high performance, 
	/// scalable best practices for common uses of SqlClient.
	/// </summary>
	public abstract class SQLHelper 
	{
		
		//Database connection strings
		//public static readonly string CONN_STRING_NON_DTC = ConfigurationSettings.AppSettings["SQLConnString"];
		//public static readonly string CONN_STRING_DTC_INV = ConfigurationSettings.AppSettings["SQLConnString"];
		public static /*readonly*/ string CONN_STRING = ConfigurationSettings.AppSettings["ConnectionString"];//ConnectionInfo.DecryptDBConnectionString(ConfigurationSettings.AppSettings["SQLConnString3"]);
		
		// Hashtable to store cached parameters
		private static Hashtable parmCache = Hashtable.Synchronized(new Hashtable());

		/// <summary>
		/// Execute a SqlCommand (that returns no resultset) against the database specified in the connection string 
		/// using the provided parameters.
		/// </summary>
		/// <remarks>
		/// e.g.:  
		///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
		/// </remarks>
		/// <param name="connectionString">a valid connection string for a SqlConnection</param>
		/// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
		/// <param name="commandText">the stored procedure name or T-SQL command</param>
		/// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
		/// <returns>an int representing the number of rows affected by the command</returns>
		
		
		public static int ExecuteNonQuery(string connString, CommandType cmdType, string cmdText, params SqlParameter[] cmdParms) 
		{

			SqlCommand cmd = new SqlCommand();

			using (SqlConnection conn = new SqlConnection(connString)) 
			{
				PrepareCommand(cmd, conn, null, cmdType, cmdText, cmdParms);
				int val = cmd.ExecuteNonQuery();
				cmd.Parameters.Clear();
				return val;
			}
		}


		/// <summary>
		/// 通过传入的参数执行插入，并返标识符的值
		/// </summary>
		/// <param name="connString"></param>
		/// <param name="cmdType"></param>
		/// <param name="cmdText"></param>
		/// <param name="cmdParms"></param>
		/// <returns></returns>
		public static int ExecuteReturnIdentity(SqlConnection conn, CommandType cmdType, string cmdText, params SqlParameter[] cmdParms)
		{
			SqlCommand cmd = new SqlCommand();
			
			PrepareCommand(cmd,conn,null,cmdType,cmdText,cmdParms);
			int val = cmd.ExecuteNonQuery();
			if(val >0)
				return (int)cmd.Parameters["@Identify"].Value;
			else
				return 0;

		}
		/// <summary>
		/// Execute a SqlCommand (that returns no resultset) against an existing database connection 
		/// using the provided parameters.
		/// </summary>
		/// <remarks>
		/// e.g.:  
		///  int result = ExecuteNonQuery(conn, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
		/// </remarks>
		/// <param name="conn">an existing database connection</param>
		/// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
		/// <param name="commandText">the stored procedure name or T-SQL command</param>
		/// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
		/// <returns>an int representing the number of rows affected by the command</returns>
		public static int ExecuteNonQuery(SqlConnection conn, CommandType cmdType, string cmdText, params SqlParameter[] cmdParms) 
		{

			SqlCommand cmd = new SqlCommand();

			PrepareCommand(cmd, conn, null, cmdType, cmdText, cmdParms);
			int val = cmd.ExecuteNonQuery();
			cmd.Parameters.Clear();
			return val;
		}

		/// <summary>
		/// Execute a SqlCommand (that returns no resultset) using an existing SQL Transaction 
		/// using the provided parameters.
		/// </summary>
		/// <remarks>
		/// e.g.:  
		///  int result = ExecuteNonQuery(trans, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
		/// </remarks>
		/// <param name="trans">an existing sql transaction</param>
		/// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
		/// <param name="commandText">the stored procedure name or T-SQL command</param>
		/// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
		/// <returns>an int representing the number of rows affected by the command</returns>
		public static int ExecuteNonQuery(SqlTransaction trans, CommandType cmdType, string cmdText, params SqlParameter[] cmdParms) 
		{
			SqlCommand cmd = new SqlCommand();
			PrepareCommand(cmd, trans.Connection, trans, cmdType, cmdText, cmdParms);
			int val = cmd.ExecuteNonQuery();
			cmd.Parameters.Clear();
			return val;
		}

		/// <summary>
		/// Execute a SqlCommand that returns a resultset against the database specified in the connection string 
		/// using the provided parameters.
		/// </summary>
		/// <remarks>
		/// e.g.:  
		///  SqlDataReader r = ExecuteReader(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
		/// </remarks>
		/// <param name="connectionString">a valid connection string for a SqlConnection</param>
		/// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
		/// <param name="commandText">the stored procedure name or T-SQL command</param>
		/// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
		/// <returns>A SqlDataReader containing the results</returns>
		public static SqlDataReader ExecuteReader(string connString, CommandType cmdType, string cmdText, params SqlParameter[] cmdParms) 
		{
			SqlCommand cmd = new SqlCommand();
			SqlConnection conn = new SqlConnection(connString);

			// we use a try/catch here because if the method throws an exception we want to 
			// close the connection throw code, because no datareader will exist, hence the 
			// commandBehaviour.CloseConnection will not work
			try 
			{
				PrepareCommand(cmd, conn, null, cmdType, cmdText, cmdParms);
				SqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
				cmd.Parameters.Clear();
				return rdr;
			}
			catch(Exception e) 
			{
				conn.Close();
				throw e;
			}
		}
		
		/// <summary>
		/// Execute a SqlCommand that returns the first column of the first record against the database specified in the connection string 
		/// using the provided parameters.
		/// </summary>
		/// <remarks>
		/// e.g.:  
		///  Object obj = ExecuteScalar(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
		/// </remarks>
		/// <param name="connectionString">a valid connection string for a SqlConnection</param>
		/// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
		/// <param name="commandText">the stored procedure name or T-SQL command</param>
		/// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
		/// <returns>An object that should be converted to the expected type using Convert.To{Type}</returns>
		public static object ExecuteScalar(string connString, CommandType cmdType, string cmdText, params SqlParameter[] cmdParms) 
		{
			SqlCommand cmd = new SqlCommand();

			using (SqlConnection conn = new SqlConnection(connString)) 
			{
				PrepareCommand(cmd, conn, null, cmdType, cmdText, cmdParms);
				object val = cmd.ExecuteScalar();
				cmd.Parameters.Clear();
				return val;
			}
		}

		/// <summary>
		/// Execute a SqlCommand that returns the first column of the first record against an existing database connection 
		/// using the provided parameters.
		/// </summary>
		/// <remarks>
		/// e.g.:  
		///  Object obj = ExecuteScalar(conn, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
		/// </remarks>
		/// <param name="conn">an existing database connection</param>
		/// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
		/// <param name="commandText">the stored procedure name or T-SQL command</param>
		/// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
		/// <returns>An object that should be converted to the expected type using Convert.To{Type}</returns>
		public static object ExecuteScalar(SqlConnection conn, CommandType cmdType, string cmdText, params SqlParameter[] cmdParms) 
		{
			
			SqlCommand cmd = new SqlCommand();

			PrepareCommand(cmd, conn, null, cmdType, cmdText, cmdParms);
			object val = cmd.ExecuteScalar();
			cmd.Parameters.Clear();
			return val;
		}

		/// <summary>
		/// add parameter array to the cache
		/// </summary>
		/// <param name="cacheKey">Key to the parameter cache</param>
		/// <param name="cmdParms">an array of SqlParamters to be cached</param>
		public static void CacheParameters(string cacheKey, params SqlParameter[] cmdParms) 
		{
			parmCache[cacheKey] = cmdParms;
		}

		/// <summary>
		/// Retrieve cached parameters
		/// </summary>
		/// <param name="cacheKey">key used to lookup parameters</param>
		/// <returns>Cached SqlParamters array</returns>
		public static SqlParameter[] GetCachedParameters(string cacheKey) 
		{
			SqlParameter[] cachedParms = (SqlParameter[])parmCache[cacheKey];
			
			if (cachedParms == null)
				return null;
			
			SqlParameter[] clonedParms = new SqlParameter[cachedParms.Length];

			for (int i = 0, j = cachedParms.Length; i < j; i++)
				clonedParms[i] = (SqlParameter)((ICloneable)cachedParms[i]).Clone();

			return clonedParms;
		}

		/// <summary>
		/// Prepare a command for execution
		/// </summary>
		/// <param name="cmd">SqlCommand object</param>
		/// <param name="conn">SqlConnection object</param>
		/// <param name="trans">SqlTransaction object</param>
		/// <param name="cmdType">Cmd type e.g. stored procedure or text</param>
		/// <param name="cmdText">Command text, e.g. Select * from Products</param>
		/// <param name="cmdParms">SqlParameters to use in the command</param>
		private static void PrepareCommand(SqlCommand cmd, SqlConnection conn, SqlTransaction trans, CommandType cmdType, string cmdText, params SqlParameter[] cmdParms) 
		{

			if (conn.State != ConnectionState.Open)
				conn.Open();

			cmd.Connection = conn;
			cmd.CommandText = cmdText;

			if (trans != null)
				cmd.Transaction = trans;

			cmd.CommandType = cmdType;

			if (cmdParms != null) 
			{
				foreach (SqlParameter parm in cmdParms)
					cmd.Parameters.Add(parm);
			}
		}

		/// <summary>
		/// 手动添加的方法
		/// </summary>
		/// <param name="conn"></param>
		/// <param name="cmdType"></param>
		/// <param name="cmdText"></param>
		/// <param name="cmdParms"></param>
		/// <returns></returns>
		public static DataSet ExecuteDataSet(SqlConnection conn, CommandType cmdType, string cmdText, params SqlParameter[] cmdParms)
		{
			SqlCommand cmd = new SqlCommand();
			PrepareCommand(cmd,conn,null,cmdType,cmdText,cmdParms);

			DataSet ds = new DataSet();
			SqlDataAdapter da = new SqlDataAdapter();
			da.SelectCommand = cmd;

			da.Fill(ds);

			cmd.Parameters.Clear();
			return ds;
		}

		public static DataTable ExecuteDataTable(SqlConnection conn, CommandType cmdType, string cmdText, params SqlParameter[] cmdParms)
		{
			SqlCommand cmd = new SqlCommand();
			PrepareCommand(cmd,conn,null,cmdType,cmdText,cmdParms);

			DataTable dt = new DataTable();
			SqlDataAdapter da = new SqlDataAdapter();
			da.SelectCommand = cmd;

			da.Fill(dt);

			cmd.Parameters.Clear();
			return dt;
		}


	}
}